White underbase decides what's opaque
Color ink printed straight onto a mirror is translucent, so the reflection shows through it and the color looks dark or metallic. That can be the effect you want, for example a tinted logo that still reflects a little. For solid brand colors, a white layer goes under the color wherever the graphic should block the reflection. The artwork needs a separate white channel that matches the color art exactly. If the white is larger than the color, you get a white halo around the edges. If it's smaller, you get a shiny fringe.
Knock-outs keep the mirror working
Any part of the file you want reflective has to be left completely unprinted, with no white and no stray color pixels. In the file, that means areas with no ink at all, not areas filled with white on screen. Mixing these up is the most common prepress mistake on mirror jobs. White on screen often prints as white ink, which covers the exact area the customer expected to stay reflective. When we proof a mirror job we show the white channel separately for this reason.
Why the graphic seems to float
On a glass mirror the silvering is on the back and the ink is on the front, so the thickness of the glass separates them. Looking at an angle, you see the printed graphic on the surface and its reflection slightly offset behind it. Thicker glass makes the gap bigger. Thin acrylic mirror shows less of it. Designers often like this because the logo looks layered and the mirror looks deep. If the brand standard calls for a flat look, plan for thinner stock or bigger solid areas and check it on a sample before ordering a full run.
An etched look without etching
White ink printed at reduced density, sometimes with a textured clear layer on top, can look like a sandblasted or acid-etched mirror. It isn't the same thing. True etching cuts into the glass, and this sits on the surface. What it gives you is the ability to print any design, fine type, and gradients that etching can't do well, plus easier reorders when a location changes. Our spot gloss and raised texture guide explains how the texture layers are built.
